Fred & George (at the Quidditch world cup)

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No: HPFGUIDX 171571

Hi all, I'm a newbie here, so forgive me if this question has already 
been answered. I have read HP&GOF several times, and I still can't 
find the answer. I wanted to know how Fred & George were able to make 
such an unlikely bet against Ludo Bagman before the Quidditch world 
cup final.... and win. Do the twins have access to time turners, or 
did they just get lucky when they made their 'prediction'. Maybe I 
have a page missing from my book, maybe I just missed something, or 
maybe we will find out in book 7?

Looking forward to book 7,
Alan.